What research steps must you go through to use the relationship between a person's intelligence and grade average in high school so that, if you know a person's IQ, you can more accurately predict the person's grade average?

2. (a) Explain conceptually why the proportion of variance accounted for equals 1.0 with a perfect correlation. (b) Why should you expect most relationships to account for only about 9% to 25% of the variance?

3. Poindexter finds r = - 0.80 when correlating number of hours studied and number of errors made on a statistics test. He also finds r = + 0.40 between speed of taking the test and number of errors on the test. He concludes that hours studied forms twice as strong a relationship and is therefore twice as important as the speed of taking the test. (a) Why is he correct or incorrect? (b) Compare these relationships and draw the correct conclusion.

4. A researcher finds that the correlation between variable A and variable B is r = + 0.20. She also finds that the correlation between variable C and variable B is r = -0.40. Which relationship is scientifically more useful and by how much?